Oxygen-bridged binuclear tungsten complex and its preparation method and application

Abstract

Oxygen-bridged binuclear tungsten complex and its preparation method and application, the form is colorless solid crystal, belongs to the monoclinic system, the space group is I 2 / a , the unit cell parameters are: a =15.39Å; b =13.04Å; c =15.64Å;α=90°;β=99°;γ=90°; Volume =3100.70Å 3 The present invention provides a tungsten complex as a catalyst, which, in combination with the green oxidant hydrogen peroxide or oxygen, can achieve the selective oxidative coupling of various aromatic amines. This provides a simple, high-yield, and cost-effective method with important commercial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of metal coordination compound functional materials, in particular to an oxygen-bridged binuclear tungsten complex and a preparation method and application thereof. Background Art

[0002] Many synthetic methods for preparing azobenzene and azobenzene oxide have been reported. Among them, the Corma research group pioneered the use of Au / TiO2 catalysts and O2 as an oxidant to selectively oxidize aniline to azobenzene (Science 2008, 322, 1661). Secondly, Bal reported the use of a hydrothermal synthesis method to prepare CuCr2O4 nanospinel catalysts, using H2O2 as an oxidant for the oxidation of aniline to synthesize azobenzene oxide compounds (ACS Sustainable Chem. Eng. 2014, 2, 584). Using green oxidants H2O2 or O2, several catalytic systems for the oxidative coupling of aniline have been developed (Green Chem. 2015, 17, 1867; Catal. Sci. Technol. 2015, 5, 3632; Catal. Today 2020, 344, 118). However, these catalytic systems are all heterogeneous, and their catalytic efficiency and selectivity need to be improved. Furthermore, the reaction only forms a single product. In particular, the noble metal catalysts and alkaline additives result in poor functional group tolerance. In 2022, Professor Ma used zirconium hydroxide (Zr(OH)₄) as a catalyst to achieve the controlled oxidation of aniline to synthesize azobenzene or azobenzene oxide (Angew. Chem. Int. Ed. 2022, 61, e202112907). This system was also heterogeneous and the reaction temperature was high (100°C). Therefore, the development of homogeneous catalytic systems with controllable selectivity and the use of milder reaction conditions are highly worthy research topics and present significant challenges. To address these challenges, we developed a catalytic system based on the air- and water-stable oxygen-bridged binuclear tungsten complex W-1. Under mild conditions, using the green oxidant H₂O₂ / O₂, we report the first binuclear tungsten-catalyzed controlled oxidation of aniline. This method achieved the selective synthesis of the fine chemicals azobenzene and azobenzene oxide and their derivatives. This method has three characteristics: (1) a new oxygen-bridged binuclear tungsten complex is used as a catalyst; (2) the reaction does not require any additives; and (3) the oxidant used is the green oxidant H2O2 / O2, and a certain type of product (azobenzene, oxyazobenzene) can be selectively obtained by controlling the reaction conditions. Summary of the Invention

[0003] Technical Problem to be Solved: The present invention provides an oxygen-bridged binuclear tungsten complex, its preparation method, and its application as a homogeneous catalyst for the oxidation of aniline to produce high-value-added products, azobenzene and azoxybenzene. This invention utilizes a homogeneous catalytic system to achieve efficient and highly selective synthesis of the target compounds. Furthermore, the mild reaction conditions employed in this invention have promising industrial application prospects.

[0004] Technical solution: Oxygen-bridged binuclear tungsten complex, in the form of colorless solid crystals, belongs to the monoclinic system, space group is I2 / a, and the unit cell parameters are: α=90°; β=99°; γ=90°;

[0005] The above oxygen-bridged binuclear tungsten complex has the structural formula shown in W-1:

[0006]

[0007] The preparation method of the above-mentioned oxygen-bridged binuclear tungsten complex comprises the following steps according to the following reaction proportions: taking 15 mL of dry toluene, adding 1 eq WCl6 under nitrogen protection and stirring at room temperature, then adding 1 eq 4,4-dimethoxy-2,2-bipyridine ligand, and finally adding 2 eq norbornene; after stirring and reacting for 1 hour, the supernatant is aspirated, and n-hexane is added to the system for washing until the clear liquid is colorless, drained, and recrystallized using acetonitrile and ether as solvents for 12 hours to obtain complex W-1.

[0008] The application of the above oxygen-bridged binuclear tungsten complex in catalyzing the controlled oxidative coupling of aniline.

[0009] The application steps are: adding an aniline derivative, an oxidant, and a catalyst W-1 to a solvent, wherein the molar ratio of the aniline derivative, the catalyst W-1, and the oxidant is 1:0.02:(1-4), placing the mixture in a reactor, heating the mixture, and obtaining a coupling product by column chromatography; the structure of the aniline derivative is: The coupling product structural formula is:

[0010] wherein R1 = halogen or alkyl group, R2 = halogen or alkyl group.

[0011] The molar ratio of the aniline derivative, catalyst W-1, and oxidant is 1:0.02:4.

[0012] The above-mentioned oxidant is hydrogen peroxide or oxygen.

[0013] When the solvent is tetrahydrofuran, the product obtained is azoxybenzene; when the solvent is acetic acid, the product obtained is azobenzene.

[0014] The reaction was carried out at room temperature, using toluene as solvent and norbornene as reducing agent. A novel binuclear tungsten complex was prepared by introducing a pyridine coordination unit with redox properties and tungsten hexachloride. The specific synthesis steps are as follows:

[0015]

[0016] Add 15 mL of dry toluene to a 100 mL reaction bottle, add (1 eq) of WCl6 under nitrogen protection, stir at room temperature, then add (1 eq) of 4,4-dimethoxy-2,2-bipyridine ligand, and finally add (2 eq) of norbornene. Under a nitrogen atmosphere, magnetically stir the reaction for 1 hour, then treat, aspirate the yellow supernatant, add n-hexane to the system for washing until the clear liquid is colorless, and drain the solvent. Use acetonitrile / ether as a solvent for recrystallization for 12 hours to obtain crystals of complex W-1. Wherein: 4,4-dimethoxy-2,2-bipyridine is used as a ligand and tungsten hexachloride is used as a metal source. NMR data: 1 H NMR (400MHz, Acetonitrile-d3) δ9.26(d,J=6.4Hz,4H),7.95(d,J=2.5Hz,4H),7.32(dd,J=6.4,2.5Hz,4H),4.06(s,12H). 13 C NMR (101MHz, Acetonitrile-d3) δ169.94,153.47,152.43,113.32,110.47,57.10.

[0017] Using W-1 as a catalyst, a controlled oxidative coupling of various aromatic amines was achieved. An aniline derivative, an oxidant, a catalyst, and a solvent were added to a reactor and heated. The reaction was then monitored for completion using TLC thin-layer chromatography. After the reaction was complete, the aniline oxidative coupling product was obtained by column chromatography.

[0018] The reaction formula is as follows:

[0019]

[0020] Where: When forming asymmetric azobenzene, the ratio of electron-withdrawing groups to electron-donating groups in the substituents is 2:1. R1 can be -H, -Me, -F, -Cl, -Br, -Et, -CF3, -3,6-2Br, -3,6-2F, -3-CH3-4-Cl, -2-SCH3, etc. R2 can be -4-F, -4-Cl, -4-Br, -4-CF3, etc. The oxidized azobenzene product of aniline has the general formula:

[0021]

[0022] The specific products obtained can be:

[0023] Azoxybenzene products

[0024]

[0025] Aniline is oxidized to azobenzene products with the general formula:

[0026]

[0027] The specific products obtained can be:

[0028] Azobenzene products

[0029]

[0030] Asymmetric azobenzene product, general formula:

[0031]

[0032] The specific products obtained can be:

[0033] Asymmetric azobenzene products

[0034]

[0035] Beneficial Effects: This invention provides a tungsten complex as a catalyst, which, when combined with the green oxidants hydrogen peroxide or oxygen, can achieve the selective oxidative coupling of various aromatic amines. This method offers a simple, high-yield, and cost-effective approach with significant commercial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is 2b in the azoxybenzene product 1 H spectrum;

[0037] Figure 2 It is 2b in the azoxybenzene product 13 C spectrum;

[0038] Figure 3 It is 2b in the azoxybenzene product 19 F NMR spectrum;

[0039] Figure 4 It is the 2c in the azoxybenzene product 1 H spectrum;

[0040] Figure 5 It is the 2c in the azoxybenzene product 13 C NMR spectrum;

[0041] Figure 6 It is the 2d in the azoxybenzene product 1 H spectrum;

[0042] Figure 7 It is the 2d in the azoxybenzene product 13 C NMR spectrum;

[0043] Figure 8 It is the 2f in the azoxybenzene product 1 H spectrum;

[0044] Figure 9 It is the 2f in the azoxybenzene product 13 C NMR spectrum;

[0045] Figure 10 It is the 2h in the azoxybenzene product 1 H spectrum;

[0046] Figure 11 It is the 2h in the azoxybenzene product 13 C NMR spectrum;

[0047] Figure 12 It is the 2i in the azoxybenzene product 1 H spectrum;

[0048] Figure 13 It is the 2i in the azoxybenzene product 13 C NMR spectrum;

[0049] Figure 14 It is the 2i in the azoxybenzene product 19 F NMR spectrum;

[0050] Figure 15 It is the 2k in the azoxybenzene product 1 H spectrum;

[0051] Figure 16 It is the 2k in the azoxybenzene product 13 C NMR spectrum;

[0052] Figure 17 It is 2m in the azoxybenzene product 1 H spectrum;

[0053] Figure 18 It is 2m in the azoxybenzene product 13 C NMR spectrum;

[0054] Figure 19 It is the 2n in the azoxybenzene product 1 H spectrum;

[0055] Figure 20 It is the 2n in the azoxybenzene product 13 C NMR spectrum;

[0056] Figure 21 It is the 2O in the azoxybenzene product 1 H spectrum;

[0057] Figure 22 It is the 2o in the azoxybenzene product 13 C NMR spectrum;

[0058] Figure 23 It is 3a in the azobenzene product 1 H spectrum;

[0059] Figure 24 It is 3a in the azobenzene product 13 C NMR spectrum;

[0060] Figure 25 It is the 3b of azobenzene product 1 H spectrum

[0061] Figure 26 It is the 3b of azobenzene product 13 C spectrum;

[0062] Figure 27 It is the 3b of azobenzene product 19 F NMR spectrum;

[0063] Figure 28 It is the 3e in the azobenzene product 1 H spectrum;

[0064] Figure 29 It is the 3e in the azobenzene product 13 C NMR spectrum;

[0065] Figure 30 It is the 3k in azobenzene product 1 H spectrum;

[0066] Figure 31 It is the 3k in azobenzene product 13 C NMR spectrum;

[0067] Figure 32 It is 3l in the azobenzene product 1 H spectrum;

[0068] Figure 33 It is 3l in the azobenzene product 13 C spectrum;

[0069] Figure 34 It is 3l in the azobenzene product 19 F NMR spectrum;

[0070] Figure 35 It is the 3m in the azobenzene product 1H spectrum;

[0071] Figure 36 It is the 3m in the azobenzene product 13 C NMR spectrum;

[0072] Figure 37 It is the 3o in the azobenzene product 1 H spectrum;

[0073] Figure 38 It is the 3o in the azobenzene product 13 C NMR spectrum;

[0074] Figure 39 It is 5a in the azobenzene product 1 H spectrum;

[0075] Figure 40 It is 5a in the azobenzene product 13 C NMR spectrum;

[0076] Figure 41 It is the 5b of azobenzene product 1 H spectrum;

[0077] Figure 42 It is the 5b of azobenzene product 13 C spectrum;

[0078] Figure 43 It is the 5b of azobenzene product 19 F NMR spectrum;

[0079] Figure 44 It is the 5f of the azobenzene product 1 H spectrum;

[0080] Figure 45 It is the 5f of the azobenzene product 13 C NMR spectrum;

[0081] Figure 46 It is the catalyst W-1 1 H spectrum;

[0082] Figure 47 It is the catalyst W-1 13 C NMR spectrum;

[0083] Figure 48 This is a single crystal diffraction test structure diagram.

[0084] Our laboratory has previously reported this reaction using a mononuclear tungsten homogeneous catalyst (Org Lett 2023, 25, 240-245), but it was not applicable to cross-coupling between different anilines. The catalyst used in the present invention can be used for cross-coupling between different anilines, which is of great significance in the field of drug synthesis. Therefore, compared with the above-mentioned technology, the present invention has made great progress. DETAILED DESCRIPTION

[0085] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not limit the scope of protection. With reference to the specific structure of the above-mentioned selective oxidative coupling product of aromatic amine, the corresponding product is selected for example.

[0086] Example 1

[0087] Preparation of Oxygen-bridged Binuclear Tungsten Complex W-1

[0088] Add 15 mL of dry toluene to a 100 mL reaction flask, add (1 eq) of WCl6 under nitrogen protection and stir at room temperature, then add (1 eq) of 4,4-dimethoxy-2,2-bipyridine ligand, and finally add (2 eq) of norbornene. Nitrogen is introduced into a double-row tube and magnetically stirred for 1 hour, and then treated. After the yellow supernatant is aspirated, n-hexane is added to the system for washing until the clear liquid is colorless and then drained. Complex W-1 is obtained by recrystallization using acetonitrile and ether as solvents for 12 hours. NMR data: 1 H NMR (400MHz, Acetonitrile-d3) δ9.26(d,J=6.4Hz,4H),7.95(d,J=2.5Hz,4H),7.32(dd,J=6.4,2.5Hz,4H),4.06(s,12H). 13 C NMR (101MHz, Acetonitrile-d3) δ169.94,153.47,152.43,113.32,110.47,57.10.

[0089] Test method: The prepared oxygen-bridged binuclear tungsten complex W-1 was subjected to single crystal diffraction test on a BRUKER diffractometer. The test results are as follows: Figure 48 It can be seen that the present invention synthesizes a new compound with a novel structure.

[0090] Preparation of the oxidative coupling of aniline to form azoxybenzene (2b): Under a nitrogen atmosphere, 0.2 mmol of 4-fluoroaniline, 0.004 mol of W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 68% yield. Mass spectrometry data for the product are as follows: theoretical value, 235.0683; experimental value, 235.0643. 1 H NMR (400MHz, Chloroform-d) δ8.31 (dd, J=9.3, 4.8Hz, 2H), 8.24 (dd, J=9.3, 5.3Hz, 2H), 7.16 (ddd, J=9.4, 8.0, 7.4Hz, 4H). 13 C NMR(101MHz,Chloroform-d)δ165.87,163.91,163.35,161.39,144.35,140.3 9,140.36,128.15,128.06,124.68,124.58,115.94,115.88,115.71,115.66. 19 F NMR(376MHz,Chloroform-d)δ-107.93,-108.47.

[0091] Example 2

[0092] Preparation of the oxidative coupling of aniline to azoxybenzene (2c): Under a nitrogen atmosphere, 0.2 mmol of 4-methylaniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 71% yield. Mass spectrometry data for the product are as follows: theoretical value, 227.1184; experimental value, 227.1166. 1H NMR (400MHz, Chloroform-d) δ8.17(d,J=8.6Hz,2H),8.11(d,J=8.5Hz,2H),7.27(dt,J=8.7,1.1Hz,4H),2.42(d,J=10.7Hz,6H). 13 C NMR (101MHz, Chloroform-d) δ146.31,142.06,141.93,140.16,129.46,129.38,125.76,122.82,122.24,21.69,21.65,21.44,21.40.

[0093] Example 3

[0094] Preparation of the oxidative coupling of aniline to azoxybenzene (2d): Under a nitrogen atmosphere, 0.2 mmol of 4-bromoaniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in 86% yield. Mass spectrometry data for the product are as follows: theoretical value, 354.9082; experimental value, 354.9079. 1 H NMR (400MHz, Chloroform-d) δ8.17 (d, J = 9.0 Hz, 2H), 8.07 (d, J = 8.9 Hz, 2H), 7.61 (dd, J = 15.5, 9.0 Hz, 4H). 13 C NMR (101MHz, Chloroform-d) δ147.15,142.68,132.16,132.09,127.35,125.12,124.01,123.74.

[0095] Example 4

[0096] Preparation of the oxidative coupling of aniline to azoxybenzene (2f): Under a nitrogen atmosphere, 0.2 mmol of 4-ethylaniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 60% yield. Mass spectrometry data for the product are as follows: theoretical value, 255.1497; experimental value, 255.1486. 1 H NMR(400MHz,Chloroform-d)δ8.19(d,J=8.7Hz,2H),8.12(d,J=8.6Hz,2H),7.30( dd,J=8.7,1.9Hz,4H),2.71(dd,J=11.8,7.6Hz,4H),1.26(dd,J=7.6,2.6Hz,6H). 13 C NMR (101MHz, Chloroform-d) δ148.28,146.38,142.12,128.25,128.19,125.83,122.36,28.97,28.73,15.45,15.42.

[0097] Example 5

[0098] Preparation of the oxidative coupling of aniline to azoxybenzene (2h): Under a nitrogen atmosphere, 0.2 mmol of 3-bromoaniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 60% yield. Mass spectrometry data for the product are as follows: theoretical value, 354.9082; experimental value, 354.9077. 1H NMR (400MHz, Chloroform-d) δ8.43 (dt, J=23.1, 2.0Hz, 2H), 8.23 ​​(ddd, J=8.3, 2.2, 1.0Hz, 1H), 8.04 (ddd, J=8 .1,1.9,1.0Hz,1H),7.70(ddd,J=8.0,1.9,1.0Hz,1H),7.53(ddd,J=8.0,2.0,1.0Hz,1H),7.41–7.33(m,2H). 13 C NMR (101MHz, Chloroform-d) δ148.94,144.75,135.07,132.92,130.30,130.16,128.41,125.81,124.59,122.55,122.45,121.19.

[0099] Example 6

[0100] Preparation of the oxidative coupling of aniline to form azoxybenzene (2i): Under a nitrogen atmosphere, 0.2 mmol of 4-trifluoromethylaniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 78% yield. Mass spectrometry data for the product are as follows: theoretical value, 335.0619; experimental value, 335.0610. 1 H NMR (400MHz, Chloroform-d) δ8.45(dt,J=8.5,0.8Hz,2H),8.22(dt,J=8.2,0.9Hz,2H),7.81(dt,J=8.5,0.7Hz,2H),7.75(dt,J=8.5,0.7Hz,2H). 13 C NMR(101MHz,Chloroform-d)δ150.23,146.08,134.17,133.84,131.44,131.11,126.44,126.41,1 26.37,126.33,126.10,126.07,126.03,125.99,125.82,125.11,124.83,123.15,122.40,122.11. 19F NMR(376MHz,Chloroform-d)δ-62.65,-62.70.

[0101] Example 7

[0102] Preparation of the oxidative coupling of aniline to form azoxybenzene (2k): Under a nitrogen atmosphere, 0.2 mmol of 3,6-dibromoaniline, 2 mol% of W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction vial. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then purified by column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 72% yield. Mass spectrometry data for the product are as follows: theoretical value, 510.7292; experimental value, 510.7283. 1 H NMR (400MHz, Chloroform-d) δ8.38(d,J=1.7Hz,2H),8.28(d,J=1.7Hz,2H),7.87(t,J=1.7Hz,1H),7.70(t,J=1.7Hz,1H). 13 C NMR (101MHz, Chloroform-d) δ149.07,145.00,137.81,135.52,127.44,124.69,123.16,122.89.

[0103] Example 8

[0104] Preparation of the oxidative coupling of aniline to azoxybenzene (2m): Under a nitrogen atmosphere, 0.2 mmol of 4-chloro-3-methylaniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (200:1, v:v) as eluents to obtain the pure product in a 52% yield. Mass spectrometry data for the product are as follows: theoretical value, 295.0405; experimental value, 295.0415. 1H NMR (400MHz, Chloroform-d) δ8.17(dd,J=2.7,0.8Hz,1H),8.06–7.99(m,3H),7.43(dd,J=10.8,8.7Hz,2H),2.47(s,3H),2.43(s,3H). 13 C NMR (101MHz, Chloroform-d) δ146.54,142.40,138.15,137.12,136.62,135.48,129.45,129.38,128.20,124.58,124.39,121.07,20.42,20.35.

[0105] Example 9

[0106] Preparation of the oxidative coupling of aniline to form azoxybenzene (2n): Under a nitrogen atmosphere, 0.2 mmol of methyl 4-aminobenzoate, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (100:1, v:v) as eluents to obtain the pure product in a 32% yield. Mass spectrometry data for the product are as follows: theoretical value, 315.0981; experimental value, 315.0977. 1 H NMR (400MHz, Chloroform-d) δ8.28 (d, J = 9.0Hz, 4H), 8.22–8.18 (m, 4H), 3.97 (s, 6H). 13 C NMR (101MHz, Chloroform-d) δ165.31,135.57,130.83,123.67,53.54,52.96.

[0107] Example 10

[0108] Preparation of the oxidative coupling of aniline to form azoxybenzene (2o): Under a nitrogen atmosphere, 0.2 mmol of 2-(methylthio)aniline, 2 mol% W-1, 0.6 mmol of hydrogen peroxide, and 2 mL of tetrahydrofuran were added to a 10 mL reaction flask. Nitrogen was then purged through a double-tube tube and heated to 60°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (50:1, v:v) as eluents to obtain the pure product in a 96% yield. Mass spectrometry data for the product are as follows: theoretical value, 315.0981; experimental value, 315.0977. 1 H NMR(400MHz,Chloroform-d)δ7.70(ddd,J=8.1,1.6,0.4Hz,2H),7.34(ddd,J=8.2,7.2,1.6 Hz, 2H), 6.80 (ddd, J=8.1, 7.2, 1.1Hz, 2H), 6.74 (ddd, J=8.2, 1.1, 0.4Hz, 2H), 3.04 (s, 6H). 13 C NMR (101MHz, Chloroform-d) δ146.32,135.40,135.29,135.17,129.51,129.43,122.00,118.10,118.02,117.75,117.71,42.35,42.19.

[0109] Example 11

[0110] Preparation of azobenzene (3a) from the oxidative coupling of aniline: 0.2 mmol of aniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added to a 10 mL reaction flask under an oxygen atmosphere. Oxygen was then introduced through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (250:1, v:v) as eluents to obtain the pure product in a 97% yield. Mass spectrometry data for the product are as follows: theoretical value, 183.0922; experimental value, 183.0913. 1 H NMR (400MHz, Chloroform-d) δ7.93 (d, J=1.6Hz, 2H), 7.91 (dd, J=1.9, 1.0Hz, 2H), 7.54–7.45 (m, 6H). 13C NMR (101MHz, Chloroform-d) δ152.74,131.10,129.20,122.94.

[0111] Example 12

[0112] Preparation of azobenzene (3b) from the oxidative coupling of aniline: In an oxygen atmosphere, 0.2 mmol of 4-fluoroaniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added to a 10 mL reaction flask. Oxygen was then introduced through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (250:1, v:v) as eluents to obtain the pure product in a 76% yield. Mass spectrometry data for the product are as follows: theoretical value, 219.0734; experimental value, 219.0728. 1 H NMR (400MHz, Chloroform-d) δ7.91 (dd, J=9.0, 5.2Hz, 4H), 7.19 (dd, J=9.1, 8.2Hz, 4H). 13 C NMR (101MHz, Chloroform-d) δ165.72,163.22,149.08,149.05,124.96,124.87,116.29,116.06. 19 F NMR(376MHz,Chloroform-d)δ-109.13.

[0113] Example 13

[0114] Preparation of azobenzene (3e) from the oxidative coupling of aniline: In an oxygen atmosphere, 0.2 mmol of 4-bromoaniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added to a 10 mL reaction flask. Oxygen was then bubbled through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (250:1, v:v) as eluents to obtain the pure product in a 71% yield. Mass spectrometry data for the product are as follows: theoretical value, 338.9132; experimental value, 338.9128. 1H NMR (400MHz, Chloroform-d) δ7.78 (d, J = 8.8 Hz, 4H), 7.64 (d, J = 8.7 Hz, 4H). 13 C NMR(101MHz,Chloroform-d)δ151.23,132.51,125.87,124.53.

[0115] Example 14

[0116] Preparation of azobenzene (3k) from the oxidative coupling of aniline: To a 10 mL reaction flask, 0.2 mmol of 3,6-dibromoaniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added under an oxygen atmosphere. Oxygen was then bubbled through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed and the reaction was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (250:1, v:v) as eluents to obtain the pure product in a 72% yield. Mass spectrometry data for the product are as follows: theoretical value, 494.7343; experimental value, 494.7334. 1 H NMR (400MHz, Chloroform-d) δ8.00 (d, J = 1.8 Hz, 4H), 7.79 (d, J = 1.8 Hz, 2H). 13 C NMR (101MHz, Chloroform-d) δ153.34,136.83,125.29,123.66.

[0117] Example 15

[0118] Preparation of azobenzene (3l) from the oxidative coupling of aniline: In an oxygen atmosphere, 0.2 mmol of 3,6-difluoroaniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added to a 10 mL reaction flask. Oxygen was then bubbled through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (250:1, v:v) as eluents to obtain the pure product in a 60% yield. Mass spectrometry data for the product are as follows: theoretical value, 255.0545; experimental value, 255.0537. 1H NMR (400MHz, Chloroform-d) δ7.47 (dd, J=7.8, 2.4Hz, 4H), 7.00–6.93 (m, 2H). 13 C NMR (101MHz, Chloroform-d) δ164.64,164.51,162.15,162.02,153.86,107.13,106.88,106.73,106.66,106.62,106.54,106.47. 19 F NMR(376MHz,Chloroform-d)δ-108.22.

[0119] Example 16

[0120] Preparation of azobenzene (3m) from the oxidative coupling of aniline: To a 10 mL reaction flask, 0.2 mmol of 4-chloro-3-methylaniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added under an oxygen atmosphere. Oxygen was then bubbled through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (250:1, v:v) as eluents to obtain the pure product in a 65% yield. Mass spectrometry data for the product are as follows: theoretical value, 279.0456; experimental value, 279.0463. 1 H NMR (400MHz, Chloroform-d) δ7.77(dd,J=2.4,0.8Hz,2H),7.68(ddd,J=8.5,2.4,0.6Hz,2H),7.46(d,J=8.4Hz,2H),2.46(s,6H). 13 C NMR (101MHz, Chloroform-d) δ150.98,137.37,137.14,129.86,125.10,121.73,20.33.

[0121] Example 17

[0122] Preparation of azobenzene (3o) from the oxidative coupling of aniline: In an oxygen atmosphere, 0.2 mmol of 2-(methylthio)aniline, 2 mol% W-1, 0.4 mmol of hydrogen peroxide, and 2 mL of acetic acid were added to a 10 mL reaction flask. Oxygen was then bubbled through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether and ethyl acetate (50:1, v:v) as eluents to obtain the pure product in a 94% yield. Mass spectrometry data for the product are as follows: theoretical value, 275.0677; experimental value, 275.0669. 1 H NMR(400MHz,Chloroform-d)δ7.24–7.19(m,4H),6.75–6.66(m,4H),2.90(s,6H). 13 C NMR (101MHz, Chloroform-d) δ147.60,132.61,132.56,126.50,126.43,123.55,117.74,117.63,38.25,38.20,38.18,38.14.

[0123] Example 18

[0124] Preparation of asymmetric azobenzene product (5a) via oxidative coupling of different anilines: 0.2 mmol aniline, 0.4 mmol 4-chloroaniline, 2 mol% W-1, 0.6 mmol hydrogen peroxide, and 2 mL acetic acid were added to a 10 mL reaction flask under an oxygen atmosphere. Oxygen was then introduced through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The organic phases were combined, dried over anhydrous MgSO₄ for 30 minutes, and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether as the eluent to obtain the pure product in an 83% yield. Mass spectrometry data for the product are as follows: theoretical value, 217.0533; experimental value, 217.0527. 1 H NMR (400MHz, Chloroform-d) δ7.92–7.88(m,2H),7.87(d,J=8.7Hz,2H),7.51(d,J=7.8Hz,2H),7.48(d,J=8.8Hz,3H). 13C NMR (101MHz, Chloroform-d) δ152.54,151.06,137.01,131.41,129.37,124.30,124.23,123.25,123.03,122.82.

[0125] Example 19

[0126] Preparation of asymmetric azobenzene product (5b) via oxidative coupling of different anilines: 0.2 mmol aniline, 0.4 mmol 4-fluoroaniline, 2 mol% W-1, 0.6 mmol hydrogen peroxide, and 2 mL acetic acid were added to a 10 mL reaction flask under an oxygen atmosphere. Oxygen was then introduced through a double-tube tube and heated to 55°C in an oil bath with magnetic stirring for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The organic phases were combined, dried over anhydrous MgSO₄ for 30 minutes, and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether as the eluent to obtain the pure product in a 71% yield. Mass spectrometry data for the product are as follows: theoretical value, 201.0828; experimental value, 201.0820. 1 H NMR (400MHz, Chloroform-d) δ7.94–7.88(m,4H),7.56–7.43(m,2H),7.22–7.17(m,3H). 13 C NMR (101MHz, Chloroform-d) δ165.73,163.22,152.55,149.06,131.15,129.22,124.89,122.91,116.13. 19 FNMR(376MHz,Chloroform-d)δ-109.11.

[0127] Example 20

[0128] Preparation of asymmetric azobenzene products (5f) via oxidative coupling of various anilines: 0.2 mmol 4-methylaniline, 0.4 mmol 4-bromoaniline, 2 mol% W-1, 0.6 mmol hydrogen peroxide, and 2 mL acetic acid were added to a 10 mL reaction flask under an oxygen atmosphere. The mixture was then heated to 55°C in an oil bath with magnetic stirring, flowing oxygen through a double-tube tube, and allowed to react for 12 hours. The oil bath was removed, and the reaction mixture was terminated by adding 1 mL of water. The mixture was extracted three times with 2 mL of ethyl acetate. The combined organic phases were dried over anhydrous MgSO₄ for 30 minutes and filtered. The filtrate was concentrated using a rotary evaporator and then column chromatography using petroleum ether as the eluent to obtain the pure product in a 70% yield. Mass spectrometry data for the product are as follows: theoretical value, 275.0184; experimental value, 275.0177. 1H NMR(400MHz,Chloroform-d)δ7.81(d,J=8.3Hz,2H),7.77(d,J=8.8Hz,2H),7.63(d,J=8.8Hz,2H),7.31(dt,J=8.0,0.7Hz,2H),2.43(s,3H). 13 C NMR(101MHz,Chloroform-d)δ151.51,150.69,142.10,132.38,129.92,125.10,124.34,123.06,21.66,21.63。

Claims

1. An oxygen-bridged binuclear tungsten complex, characterized in that: The morphology is colorless solid crystal, belongs to the monoclinic system, the space group is I2 / a, and the unit cell parameters are: α=90°; β=99°; γ=90°; The structural formula is shown in W-1:

2. The method for preparing the oxygen-bridged binuclear tungsten complex according to claim 1, characterized in that: The steps according to the following reaction proportions are: take 15 mL of dry toluene, add 1 eq WCl6 under nitrogen protection and stir at room temperature, then add 1 eq 4,4-dimethoxy-2,2-bipyridine ligand, and finally add 2 eq norbornene; after stirring and reacting for 1 hour, the supernatant is aspirated, n-hexane is added to the system for washing until the clear liquid is colorless, and then dried, and recrystallized using acetonitrile and ether as solvents for 12 hours to obtain crystals of complex W-1.

3. Use of the oxygen-bridged binuclear tungsten complex according to claim 1 in catalyzing the controlled oxidative coupling of aniline, characterized in that: The steps are: adding an aniline derivative, an oxidant, and a catalyst W-1 to a solvent, wherein the molar ratio of the aniline derivative, the catalyst W-1, and the oxidant is 1:0.02:(1-4), placing the mixture in a reactor, heating the mixture, and obtaining an analytically pure coupling product after column chromatography separation; the structure of the aniline derivative is: The coupling product structural formula is: Wherein R=R1 or R2, R1=halogen or alkyl group, R2=halogen or alkyl group.

4. The use according to claim 3, characterized in that The molar ratio of the aniline derivative, catalyst W-1, and oxidant is 1:0.02:

4.

5. The use according to claim 3, characterized in that The oxidant is hydrogen peroxide or oxygen.

6. The use according to claim 3, characterized in that When the solvent is tetrahydrofuran, the product obtained is azoxybenzene; When the solvent is acetic acid, the product obtained is azobenzene.

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